From DE 10 2008 034 430 A1 a generic method is known for the production of a piston composed of a piston upper part and a piston lower part of an internal combustion engine, in which the piston upper part is welded via a contact surface with the piston lower part and thereby a cooling duct is formed which is situated therebetween. To introduce a coolant into the cooling duct, a flow tube which is inserted into the piston lower part and projects from a cooling channel base is arranged in an inlet opening, the opening of which flow tube is arranged above welding beads of the friction-welded connection. In this installation position, the flow tube is fixed in position in the region of the contact geometry on both sides partially by the welding beads which occur during the friction-welded connection. The flow tube which is inserted remains in the piston after the production of the friction-welded connection and ensures an unrestricted cross-section in the region of the inlet opening.
A disadvantage from the prior art is that to keep the inlet opening free, firstly the flow tube which is able to be inserted into the piston lower part must be mounted and adjusted, resulting in assembly costs which are not to be underestimated. At the same time, the flow tube, which of course can also be positioned in the same way in an outlet opening of the cooling duct, requires storage and logistics expenses which are not to be underestimated.